This was due to changes in the fraction of CTLA4 expressing Teff cells since this cell subpopulation decreased significantly at late time points after seed implantation (24 months: 1.25% mean with 0.96–1.54% 95% CI and 36 months: 0.71% mean with 0.49–0.93% 95% CI) compared to both healthy controls (1.96% mean with 1.02–2.91% 95% CI) and prostate cancer patients before seed implantation (2.53% mean with 1.09–3.96% 95% CI) (Figure 3B). Here, CTLA4 is linked to prostate carcinoma.